Scientists can now turn pollution into solid rock

A
manager at a test well at Reykjavik Energy's Hellisheidi
geothermal power plant in Iceland.Brennan Linsley/AP

When it comes to dealing with human-caused carbon dioxide (CO2)
emissions, one of the more ambitious but still largely unproven
fixes could be carbon capture, which sucks CO2 out of the
atmosphere or from industrial plants.

Two of the biggest problems with carbon capture have been its cost, and finding ways to
efficiently store or repurpose the CO2 once it's been extracted.
But now a new technique could drastically overhaul this method of
mitigating climate change: turning carbon emissions into solid
rock.

An international team of scientists working in Iceland has
successfully demonstrated that CO2 emissions can be pumped
underground and altered chemically to form solid stone. While
storing carbon in the earth is not a new thing, nobody ever
expected the process to work this quickly or efficiently.

In a new study published in Science, the researchers explain that their
technique for turning atmospheric carbon into solid rock only
takes a few months — a timeframe that could finally help make
carbon capture and storage a practical, workable solution.

"This means that we can pump down large amounts of CO2 and store
it in a very safe way over a very short period of time," said hydrologist Martin Stute from Columbia
University.

Brennan
Linsley/AP

The researchers began their CarbFix project at the Hellisheidi
power plant – the world's largest geothermal facility. They mixed
carbon dioxide and hydrogen sulphide produced by the plant with
water, and injected it into the volcanic basalt underneath the
plant.

When basalt is exposed to CO2 and water, the carbon precipitates
into a white, chalky solid, but in these kinds of conditions,
nobody knew how long the process might take.

Initial estimates suggested that the process could take between
eight to 12 years, but in this case, the conversion began to take
place in a matter of months.

"Our results show that between 95 and 98 percent of the injected
CO2 was mineralised over the period of less than two years, which
is amazingly fast," said geoengineer and lead researcher Juerg
Matter from the University of Southampton in the UK.

After a successful pilot in 2012, the plant has continued
injecting carbon dioxide underground, and ongoing monitoring
suggests the mineralisation process is keeping on consistently
and safely — which could calm fears that storing CO2 underground
might be dangerous.

"Carbonate minerals do not leak out of the ground, thus our newly
developed method results in permanent and environmentally
friendly storage of CO2 emissions," said Matter. "On the other hand, basalt is one
of the most common rock types on Earth, potentially providing one
of the largest [means of] CO2 storage capacity."

The researchers haven't yet indicated whether there could be any
potential use for the carbon rocks once they've been made, which
is something other carbon capture techniques have looked into.

So there are plenty of alternatives if long-term storage in rock
underground doesn't work out, but right now it sounds like this
new technique could turn out to be a huge deal for carbon capture
and storage – and climate change mitigation more generally.

But the team acknowledges there's still a lot more research to be
done. The process also requires large amounts of water to work,
but the researchers say seawater could be used.

"The overall scale of our study was relatively small. So, the
obvious next step for CarbFix is to upscale CO2 storage in
basalt," said Matter. "This is currently happening at
Reykjavik Energy's Hellisheidi geothermal power plant, where up
to 5,000 tonnes of CO2 per year are captured and stored in a
basaltic reservoir."

It's early days, sure, but we can't wait to see where this
research leads.